Method for separating glass sheets and the like



June 12', 1945- J. A. M CORMICK, JR 2,378,091

METHOD FOR SEPARATING GLASS SHEETS AND THE LIKE ori inal Filed Nov, 29, 1941 45 I INVENTOR. JasyhZ/ycbrm'cgfr, BY 4 I Patented June 12, 1945 METHOD FOR SEPAR v AND ATING GIASS SHEETS THELIKE Joseph A. McCormick, 11 ForestPark, 111., as-

signor to Dearborn Glass Company, Chicago, 11., a corporation of Illinois I Original application November 29, 1941, Serial No. i20,916. Divided and this application June 5, 1944, Serial No. 538,725

3 Claims.

My invention relates to a method of separating a sheet of glass or other vitreous material in two separate integral parts. present method is especially adapted for forming openings in sheets of glass or the like.

The present application is a. division of myap- \plication Serial No. 420,916, filed November 29, 1941, now issued as patent No. 2,372,215, dated March 2'7, 1945, the latter application being a continuation-in-part of my earlier application Serial No. 362,809, filed October 25, 1940-, now issued as patent No. 2,329,922, dated September 21, 1943.

It has long been the practice in the art to-form openings in glass sheets bya grindingoperation. This method is unsatisfactory for many reasons.

For example, in grinding an opening the sheet must be turned over since it must be ground inwardly from both top and bottom surfaces to prevent chipping of the surfaces of the glass sheet More particularly, the

adjacent the marginal edge defining the opening. 'Even if great care is exercised there nevertheless will be slight chipping of the glass surfaces. Grinding, at best, is a slow and expensive process. The marginal edge defining the opening will be roughened and if the glass sheet is tube used for decorative purposes in which this edge is exposed, a polishing operation is necessary. It has been my experience that this method is not economically feasible from a manufacturing standpoint. In addition this method lends itself only to the formation of circular openings.

It is an object of my invention to provide a method for readily separating a glass sheet into two integral portions, in which one portion of the glass sheet initially is substantially included tel lithn or surrounded by the other portion of the s cc A further object is;-to provide a method for. readily forming openings of any. desired con- In order to attainthe above objects I propose to score opposite surfaces of the glass sheet with the scoring on the surface being similar in outline but in which the" scoring on one surface lies glass sheet then is preferably fleired slightly by hand to produce a tapered fracture extending through the thickness of the sheet. I have found.

tion of the fracture in advance of heating is not absolutely essential in practicing my invention.

Now, it will appear that since the sheet can be readily separated into two separate integral portions either of the portions may constitute theproduct. Thus, the invention is adaptable for forming glass sheets of intricate contour in which the portion within the score line constitutes the product, or if desired, the outer portion I may constitute the product. In either case, shattering of either portion of the glass sheet is avoided.

So far as I am aware the principle of effecting separation ofv a glass sheet along a tapered fracture in the sheet by causing a relative change in dimensions between the portions defined by the fracture is broadly new. It will be understood that'the application of the principle to a' glass sheet is illustrative and not limiting, since the method disclosed may be adaptable for use with materials other than glass.

Now in order to acquaint those skilled in the 4 art with the manner of utilizing my invention, I

shall disclose in conjunction with the accompanying drawing a specific embodiment of the same.

In the drawing: w Figure 1 is a plan view of a sheet of glass stock which has been scored to provide a number of small circular sheets Figure 2 is a plan view of one of the smaller circular sheets of Figure 1;

Figure 3'is a; side elevational view of one suitable means for supporting the circular sheet of Figure 2 in a furnace, the furnace being shown in- 4 section and somewhat diagrammatically;

Figure 4 is a sectional view of the supporting means of Figure 3 and showing inv section, the

in'ner and outerportions of the circular glasssheet separated from each other;

Figure-5 isa cross-sectional view of;a glass sheet which has been scored on bothsurfaces and flexed to cause the tapered fracture;

within the scoring on the other surface. The Figured is a sectional view through a glass sheet which has been scored in the manner shown in Figure 5 and after the inner portion of the sheet has been removed; and

Figure 7 is a plan view of a substantially square sheet having a substantially square opening which may be formed by the method of the present invention.

Referring now to Figure l, I have shown a sheet of fiat glass stock 2 which has been scored, at 3, by means of a suitable glass cutter to outline a number of small circular glass sheets 35,

one of which is shown in Figure 2, which one isobtained by breaking away the glass sheet 2 outside of scoring 3.

As shown in Figure 5 one surface of one of the sheets 35 is scored as at 38 with a suitable scoring tool to define a circular score line of a diameter a. The sheet is then turned over and the other surface is scored, as at 31, in a suitable manner so this circular score line is of a diameter b, in which diameter b is somewhat less than the diameter it. Now if the sheet 35 is grasped and slightly flexed as shown in Figure 5, as by grasping opposite marginal edges of the sheet by the hands and. exerting force in opposed directions, as illustrated, a fracture or run will extend from the score line 36 to the score line 31 to produce a tapered fracture 38. When it is desired to treat azsheet of double strength glass, i. e., of from 115 to .140 thousandths of an inch thick, I have found that subsequent separation of the inner and outer portions 39 and 40, of Figure 5, from each other may be readily attained if the sheet is suitably scored so that diameter b is approximately .016 of an inch less than the diameter a, of the sheet of this figure so that thetaper 33 extends substantially at an angle of approximately 4, from the perpendicular. may, however, be larger or smaller and satisfactory separation is secured if the angle is within the. range of 3 to 10.

In Figures 3 and 4, I have shown an apparatus suitable for carrying outthe practice of the present method. .'A metal block I 2 is provided is substantially the same as or slightly less than The angle of the fracture core portion 39, and be received by the annular seat 20 of the block l2.

After the portions 39 and 40 have been separated from each other, the block I! is removed from the furnace and the separated glass pieces removed therefrom, after which another circular lass sheet 35 may be positioned upon the projection l3 and inserted in the furnace to repeat the operation. The rotation of the sheet past the flame is not essential. It is merely a suitable way of getting the outer portion 40 heated up is placed upon the heated blo'ck l2, the core por- 1 tion will not expand the sheet and break it before the temperature of the outer ring portion 40 can be raised to an appropriate degree and the proper temperature differential established between portions 39 and 40 of the sheet. Alternate means for causing separation of the two portions may be readily devised in which the outer rin portion 40 supportsthe glass sheet and upon creating a difference in temperature of the portions 39 and 40, the core portion 38 will drop away from the supported sheet.-

Glass known in the trade as 16 oz. glass and of a thickness of 60 to 83 thousandths of an inch may be readily separated when scored and fractured, as described, by disposing the sheet in an oven at a temperature of approximately 1000 F. for about 1 min. and 10 sec. A sheet of single strength glass i. e. of 83 to 103 thousandths of an inch in thicknessmay be separated in two integral portions in approximately one min. and 30 sec. at an oven temperature of 1000 F.. In practicing the method with double strength glass, i. e. of approximately 110 to 140 thousandths of an inch in thickness, I have found that an oven temthe diameter of the core portion 33; A piece of heat insulating-material I ijsuch as asbestos, is

disposed upon the upper surface 4 of the core sheet. The furnace I! may be designed to readily eil'ect preheating of the glass sheet or other means may be employed, as desired. Rotation of the glass sheet inthe flame ll gradually increases the temperature of the outer ring portion 40 to-a reater extent than that of core portion 33. If

desired, a plurality of gasgiurners may be' employed for heating the furnace and the r portion". o o

,Theinsulating material ll shields the core portion 33 from' the fla ne I8, and the annular projection l 3," -by conduction, serves -.to maintainthe core portion at a'lower temperature than the perature of approximately 1000 F. the glass sheet is separated in approximately 1 min. 45 sec. In all of theabove referred to specific preferred examples of my invention it is estimated that the portion of the glass sheet surrounding th score line attains a temperature of approximately 175 to 200 F. It will be understood that these examples are given merely as illustrative since it is believed that a wide variation may be made between oven temperatures and in the length of time required to attain the separation without departing from the broader concept of my invention.

n gure 6, there is shown a glass sheet 45 having an opening 46 formed therein by the method as described in connection with Figure 5.

r The resultant tapered edge defining the opening I6 is not readily discernible and for all practical purposes is unobjectionable. Preferably, however, where glass sheets having openings are to .be used for decorative purposes, the scoring should be controlled so that the angle of taper of the edge does not exceed substantially 10. It will be obvious, however, that if a distinct visible taper is desired that may be accomplished by creating a lar e difference indiameter between-the dimensions a and b of Figure 5.

' It will be appment that the invention may be practiced to form openings of any desired con,

figuration, and in Figure 7 I have shown a Square sheet of glass 26 having a square opening 21 '1 ring portion. 40. As the ring portion 43 is heated formed therein by my above described method.

' itwill expand and finally drop, away from the 76' Heat, may be extracted from the inner portions at the sametiine that heat is added to the outer portions if desired. The whole sheet may be heated and the center cooled or the whole sheet may be cooled and the outside portions heated as may be desired.

Obviously, if desired, the above method and apparatus; may be employed for forming glass sheets of intricate contour, in which event the portion within the score lin'e comprises the product.

While I have described the method of the present invention in connection with flat sheet glass, it will be readily obvious to those skilled in the art that my method is readily adaptable for forming clamopenings in curved sheets of glass.

1. The method of separating an outer part of a glass sheet or the like from an inner part thereof which is substantially included within the outer part, comprising scoring opposite surfaces of the sheet with the scoring on one surface lying within the-scoring of the other surface to define said inner partv along lines extending 2. The method of separating anouter-part of a glass sheet or the like from an inner part thereof which is substantially v included within the outer part,comprising scoring opposite surfaces of the sheet with the scoring on one surface lying within the scoring of the other surface to define said inner part along lines extending through and converging inwardly of saidsheet from one of the surfaces thereof, flexing said sheet to fracture the same from the scoring on one surface to the scoring on the other surface whereby the juxtaposed edges of said parts after fracture will be tapered, supporting the entire sheet through the support of one-of said parts, and thermally expanding said outer part at a-faster rate than said inner part to separate the parts from each other along the fracture.

3. The method of separating an outer part of a glass sheet or the like from an inner part thereof which is substantially included within the outer part comprising, scoring opposite surfaces of the sheet with the scoring on one urface lying within the scoring on the other surface to define said inner part along lines extending through and converging inwardly of said sheet from one of the surfaces thereof whereby the juxtaposed edges of said parts after fracture will be tapered,

and'expanding said outer part more than said inner part to separate the same; I

' JOSEPHAJMcCORmCK, JR. 

